Numerical simulation of natural convection in mixed porous/pure-fluid domains

This thesis is dedicated to the exploration of natural convection phenomena within domains characterized by a heat-generating porous matrix immersed in a pure-fluid region. Such flows hold particular significance in the context of Loss-of-Cooling Accidents (LOCA) occurring within Spent Fuel Pools (SFP) in nuclear power plants. In this application, the porous medium models the fuel assemblies placed in storage racks at the pool's base. During a LOCA event, the cooling circuit, which maintains low temperatures in the pool, becomes inoperative, leading to a free convection regime within the pool. The Fukushima accident in 2011 exposed our limited comprehension of the intricate processes that take place during LOCA. This work aims to address this problem by producing accurate data on the fundamental physics governing the flow dynamics and heat transfer in this context. This objective is of great interest to the research community involved in industrial numerical simulations of SFP during LOCA scenarios. To achieve these goals, we have developed a numerical tool for conducting Direct Numerical Simulations of three-dimensional natural convection within porous/pure-fluid domains. The tool has been validated and verified against a large set of cases, and its numerical properties have been studied. We perform an analysis on the parameters that drive the physical modeling of the porous medium, providing valuable insights into the flow dynamics and heat transfer in such a configuration. The investigation extends to exploring the effects of altering rack heights relative to the bottom wall as well as the consequences of uneven heat load distribution within the racks. This examination provides valuable insights and paves the way for an enhanced understanding of LOCA phenomena.